This invention relates generally to sockets for removably mounting electronic packages, such as a package containing an integrated circuit, for conducting electrical tests of such packages and more particularly to such sockets in which each conductive terminal of an electronic package is electrically connected to a respective lead in the socket for further connection to testing equipment.
IC (integrated circuit) packages in which an IC chip has been sealed by resin are typically subjected to a reliability test called a burn-in test to separate them into satisfactory and unsatisfactory products.
FIGS. 13(a)-13(d) show an example of a known socket 101 used in burn-in tests for electronic packages having BGA (Ball Grid Array) terminals. Socket 101 has a square-shaped base 102 in which are mounted a plurality of contacts 104 for a pressure connection of respective solder balls 100a of a BGA package 100. Contacts 104 are each made of an elongated metal member, with a pair of arms 104a and 104b being provided at one end thereof. A slider 105 capable of carrying BGA package 100 is mounted on base 102 for movement in the horizontal direction (X direction). Slider 105 is adapted to accommodate contacts 104 through contact receiving holes 105a. As shown in FIGS. 13(a), 13(b), respective ball receiving holes 105c for accommodating each solder ball 100a are formed on seat 105b of slider 105 in such a manner as to cross the contact accommodation hole 105a. As shown in FIG. 13(b), further, respective engagement parts 105d of slider 105 are formed inside of contact receiving holes 105a for engagement with arms 104a of respective contacts 104. A cover 106 for operating slider 105 is provided on base 102 for movement toward and away from base 102 through compression coil springs 107.
In a socket as described above, if cover 106 is pressed down, slider 105 moves in the X+ direction, causing arms 104a of contacts 104 to engage with engagement parts 105d of slider 105, thereby opening the contacts in the X+ direction in a bent state. When, in this state, the BGA package 100 is dropped onto seat 105b of slider 105, each solder ball 100a of BGA package 100 is accommodated in a respective ball receiving hole 105c. When cover 104 is raised, slider 105 is returned in the Xxe2x88x92 direction by the force of arms 104a of contacts 104. As a result, each arm 104a contacts a respective solder ball 100a and, at the same time, the other arm 104b bends in the Xxe2x88x92 direction as it is pushed by solder ball 100a. Each pair of arms 104a and 104b sandwich a solder ball 100a, so that each solder ball 100a of the BGA package is electrically connected to a contact 104.
In the above arrangement, arms 104a and 104b move in connection with the opening of arms 104a and the holding of the solder ball 100a by both arms 104a and 104b. Accordingly, it has been necessary to provide an area large enough to conform to the amount of movement of arms 104a and 104b in seating portion 105b of slider 105. Since there is a physical limitation as to how close contacts 104 can be arranged, it has been difficult to use a conventional socket 101 for BGA packages having solder balls that have been arranged in finer pitches.
It is an object of the present invention to solve the above noted problems of the prior art. Another object of the invention is the provision of a socket which is adaptable for use with IC packages of finer pitches.
Briefly described, a socket made in accordance with a preferred embodiment of the invention for removably receiving an electronic part having terminals arranged according to a selected pattern comprises a socket base having a plurality of contacts arranged corresponding to the selected pattern, each having a cantilever-like contact arm capable of contacting a terminal of an electronic part. A slider capable of moving in a horizontal direction relative to the socket base is slidably mounted on the base and has a plurality of contact receiving through-holes that correspond to the positions of the contact arms. The walls of the through-holes are arranged so that they apply no bias to the contact arms allowing them to function as free ends. The slider is also formed with terminal receiving holes for accommodating the terminals and which communicate with the through-holes. The terminals can be accommodated in the terminal receiving holes when the slider is at a selected position and the arms can be flexibly connected with the terminals in the terminal receiving holes when the slider is at another selected position.
According to a feature of the invention, the contacts are each formed with a single contact arm rather than the conventional pair of squeezable arms and the terminals of the electronic part are engaged in the terminal receiving holes upon movement of the slider, thereby making it possible to connect each respective terminal of the electronic part by holding such terminal between a wall, i.e., a terminal engagement surface in a terminal receiving hole, and an arm of a contact. Accordingly, only enough space need be provided on the slider which corresponds to the range of movement required for the terminals of the electronic part to be connected with the arms of the contacts under a suitable force so that the area that the contact arm occupies on the slider seat can be smaller than that provided in the prior art. As a result, terminals with a finer pitch can be accommodated. According to another feature of the invention, a cover is provided which is capable of moving in a direction toward or away from the socket base. The cover has an engagement portion capable of engaging the slider to move the slider in a selected direction as the cover moves toward or away from the socket base when the engagement portion is in engagement with the slider. In accordance with the invention, the contacts are bent only when they are engaged with terminals of the electronic part, thereby enhancing the durability of the contacts. According to another feature of the invention, the terminal engagement surface of the terminal receiving hole can be a cylindrical surface or it can be configured in greater conformity with the surface shape of the terminals of the electric part with which the socket is used, e.g., partly spherical for solder ball terminals.
According to a feature of the invention, the contacting portion of the contact arms can be formed with projections, for example, in the shape of a claw having a pair of spaced apart projections extending in selected directions so that when mounted they extend toward the terminal engagement surfaces. Thus, the contacts can be stably connected with the terminals of the electronic part in a contact area that correspond to the contact area of a plurality of arms even when a single arm is employed.
According to yet another feature, the contacting portions of the contact arm are arranged to contact the root portion of the terminals on the side of the electronic part from which the terminals extend. When used with electronic parts having a BGA package with globular terminals, the contacting portion of the contact arms engage the terminals between the bottom surface of the package and that portion of the terminals where the diameter becomes the largest relative to planes parallel to the bottom surface of the package.
According to another feature of an embodiment of the invention, a jig having a holding and releasing part for delivery of an electronic part is movable toward and away from the socket and can be used to move the cover or the slider of a socket having no cover.
Additional objects and features of the invention will be set forth in part in the description which follows and in part will be obvious from the description. The objects and advantages of the invention may be realized and attained by means of the instrumentalities, combinations and methods particularly pointed out in the appended claims.